Progesterone concentrations during estrous cycle of dairy cows exposed to electric and magnetic fields.
ABSTRACT Sixteen multiparous nonpregnant lactating Holstein cows (each weighing 662 +/- 65 kg in 150.4 +/- 40 day of lactation) were confined to wooden metabolic cages with 12:12 h light:dark cycle during the experiment. The cows were divided into two sequences of eight cows each and exposed to electric and magnetic fields (EMF) in an exposure chamber. This chamber produced a vertical electric field of 10 kV/m and a uniform horizontal magnetic field of 30 microT at 60 Hz. One sequence was exposed for three estrous cycles of 24 to 27 days. During the first estrous cycle, the electric and magnetic fields were off; during the second estrous cycle, they were on; and during the third estrous cycle, they were off. The second sequence was also exposed for three 24 to 26 days estrous cycles, but the exposure to the fields was reversed (first estrous cycle, on; second estrous cycle, off; third estrous cycle, on). The length of each exposure period (21 to 27 days) varied according to the estrous cycle length. No differences were detected in plasma progesterone concentrations and area under the progesterone curve during estrous cycles between EMF nonexposed and exposed periods (2.28 +/- 0.17 and 2.25 +/- 0.17; and 24.5 +/- 1.9 vs. 26.4 +/- 1.9 ng/ml, respectively). However, estrous cycle length, determined by the presence of a functional corpus luteum detected by concentrations of progesterone equal to or more than 1 ng/ml plasma, was shorter in nonexposed cows than when they were exposed to EMF (22.0 +/- 0.9 vs. 25.3 +/- 1.4 days).
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ABSTRACT: Electric and magnetic fields (EMF) are generated by the transmission of electricity through high tension lines traversing rural areas. Previous studies showed increased dry matter intake (DMI) and fat corrected milk in dairy cows exposed to EMF. Because EMF exposure has been shown to suppress pineal release of melatonin in some species, it was hypothesized that EMF effects resemble those of exposure to long days. Previous studies have shown that DMI and milk production increase in dairy cattle in response to long day photoperiods, and this has been observed in association with increased circulating insulin-like growth factor 1 (IGF-1), but not growth hormone (GH). The hypothesis that EMF act by modifying the response to photoperiod was tested by subjecting dairy cows to controlled EMF exposure while keeping them under short-day conditions. Sixteen lactating, pregnant Holstein cows were exposed to a vertical electric field of 10 kV/m and a horizontal magnetic field of 30 microT in a crossover design with treatment switchback. Two groups of eight cows each were exposed to EMF for 16 h/d in either oftwo sequences. Each sequence consisted of three consecutive 28-d periods. All animals were maintained under short day conditions (8 h light, 16 h dark) during the trial. DMI and plasma IGF-1 were increased (P < 0.01) during EMF exposure (17.03 vs.16.04 kg/d, SE = 0.4; 137 +/- 6 ng/ml vs 126 +/- 6, respectively). The mean GH concentration was not affected, but a treatment x hour interaction was detected, with GH lower for the EMF exposed animals during the first 16 h of the sampling period, and higher for the last 8 h. Overall, the yield of milk or its components was not affected by EMF exposure, but milk yield was significantly higher for the exposed animals during wk 4 of treatment.Journal of Dairy Science 11/2002; 85(11):2843-9. · 2.57 Impact Factor
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ABSTRACT: The effects of extremely low-frequency (ELF) magnetic fields on sex hormones of adult female Spague-Dawley rats were investigated. Adult female rats were exposed to a 50 Hz sinusoidal magnetic field at approximately 25 microT (rms) for 18 weeks before they returned to their normal life with unexposed counterparts. Serum level of Luteinizing Hormone (LH), Follicle Stimulating Hormone (FSH), progesterone, and estrogen were measured before, after, and during the exposure. Body and uterine weights were not affected by the field. A significant reduction in absolute and relative ovarian weights in exposed rats was observed when compared with sham-exposed controls (P < 0.05). The reduction in the levels of gonadotropins (FSH and LH) was significant after six weeks of exposure (P < 0.005). FSH levels were affected only on week 6 of exposure while LH remained affected during at 12 and 18 weeks (P < 0.05). Interestingly, no significant effects were found at 6 and 12 weeks after removing the field. The level of progesterone and estrogen was significantly decreased after 12 weeks of exposure (P < 0.05), while no other effects on progesterone level was observed during exposure or after removing the exposure. The level of estrogen was also significantly reduced at 12 weeks after removing the field (P < 0.05). These results suggest possible adverse effect on mammalian fertility and reproduction. The effects of ELF-MF on sex hormones were shown to be partly reversible.Electromagnetic Biology and Medicine 02/2008; 27(2):155-63. · 0.81 Impact Factor
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ABSTRACT: ZUSAMMENFASSUNG: ››› Das mögliche Risikopotential hochfrequenter elektromagnetischer Felder des Mobilfunknetzes wird seit Jahren kontrovers und emotional diskutiert. Da Mobilfunksendeanlagen häufig auf landwirtschaftlich genutzen Flächen errichtet werden, stellt sich aus tier- medizinischer Sicht die Frage, ob an landwirtschaftli- chen Nutztieren in unmittelbarer Umgebung solcher Sendeanlagen Veränderungen in Gesundheit, Leistung oder Verhalten auftreten. Diese Übersichtsarbeit stellt eine Bestandsaufnahme dieses Themas dar. Neben ei- ner Reihe von Fallbeschreibungen bei Milchrindern, Schweinen und Geflügel wird die bayerische Rinder- studie diskutiert, die trotz zum Teil gravierender Män- gel einige besorgniserregende Unterschiede zwischen hoch und niedrig exponierten Betrieben zeigte, so eine Erhöhung von Missgeburten und Verhaltensänderun- gen, die zu einem Rückgang der Milchleistung führen können. Aufgrund dieser Beobachtungen planen eini- ge Arbeitsgruppen der Tierärztlichen Hochschule Han- nover eine epidemiologische Studie zur Auswirkung elektromagnetischer Felder von Mobilfunksendeanla- gen auf Leistung, Gesundheit und Verhalten von Rin- dern. Wir erwarten von dieser Studie eine weiter- führende Klärung der Frage, ob und unter welchen Be- dingungen eine Exposition in derartigen Feldern ein Risiko für landwirtschaftliche Nutztiere darstellt und zu ökonomischen Verlusten führen kann. SUMMARY: ››› The risk potential, if any, of radiofrequency (RF) electromagnetic fields as used for cellular radio sys- tems is an ongoing topic for controversial discussion. Base stations and base station antennas transmitting RF fields are often located on or near to farms, leading to the question whether farm animals in the vicinity of such stations exhibit alterations in health, productivity or behaviour. This review surveys the available infor- mations on this topic. In addition to several case reports in dairy cattle, swine and poultry, the Bavarian cow stu- dy is discussed. Despite several logistical problems of the latter study, some alarming differences evolved between farms with high and low RF field exposure, in- cluding an increase in birth defects and behavioural al- terations in exposed cows which could lead to a reduc- tion in milk production. Based on these data, scientists of the Hannover School of Veterinary Medicine plan a large epidemiological study on the effects of RF field ex- posure on milk production, behaviour and health of dairy cows. We expect that this study will help to an- swer the question if and under which circumstances en- hanced RF field exposure poses a risk for farm animals.